Heat transfer papers for transferring letters, figures, designs, and other shapes (referred to collectively as “shapes”) to a substrate for the purpose of display and/or decoration have developed into a significant industry. When heat transfer paper is used for transferring letters, figures and designs to a substrate, there have been a variety of transfer methods. For instance, the desired shape can be printed onto the heat transfer paper, in advance, on a substrate with a thermally transferable material according to a proper printing method (e.g., silk screen printing, gravure printing, offset printing, etc.), and then the shape is transferred to the substrate. Another exemplary method includes applying a thermally transferable layer on the whole surface of the heat transfer paper, cutting out the desired shape(s) from the heat transfer paper, and then transferring the shape to a substrate using heat and pressure (e.g., applied to an ironing sheet).
Methods where the shapes are formed through printing can be suitable for preparing a large amount of heat transfer materials of the same letters or figures and designs. However, the relatively high costs and expenses involved in printing can lead to high costs per unit, especially for small scale production.
Methods where a heat transfer sheet having a thermally transferable layer applied onto the whole surface of a base which layer is cut into the desired shape can have a number of ways to apply the shapes to the substrate. In one example, the shapes can be cut fully out of the heat transfer paper (i.e., the shape is cut through the entire thickness of the heat transfer sheet), and then arranged and applied to the substrate to be transferred. However, this method can lead to inaccuracies and difficulties in exactly replicating the design when multiple shapes must be individually arranged together (e.g., multiple letters forming a word).
Alternatively, the shape can be cut into the heat transfer material only to the base sheet (i.e., leaving the base sheet intact). For example, the shape can be cut using an automatic cutting machine controlled by a computer. There have been known a variety of methods for preparing letters or patterns with such an automatic cutting machine. Then, transfer tape can be utilized to remove the shape(s) from the heat transfer material and position it (them) on the substrate. However, in this method, the areas surrounding the shape to be transferred to the substrate must be removed (i.e., weeded) from the transfer material. Then, the remaining shape on the base sheet can be lifted from the base sheet and laid onto the substrate. Thus, the tape must be able to temporarily bond to the shape, and the substrate, withstand the transfer process, and then be removable from the transferred shape and the substrate without damaging either. Such selection of tape can be difficult, and the tape can significantly increase the cost of the transfer as suitable tape can be expensive.
In another alternative method, the shape can be cut into the heat transfer material leaving the base sheet intact, and the areas surrounding the shape can be removed leaving only the shape on the base sheet. Then, the shape can be transferred to the substrate. However, removing the areas around the shape can be difficult using presently available heat transfer sheets. For example, the removal of the unnecessary portions of the transfer layer by peeling can be relatively easy when the thickness of the transfer layer which is applied onto the base sheet over a releasing layer is thick. However, such thick transfer layers can lead to overly thick shapes transferred onto the substrate and are subject to more wear over time. On the other hand, removing the unwanted portion of a thin transfer layer is difficult and can lead to deformation in the shape to be transferred.
A need exists, therefore, for an improved method of heat transfer for shapes and improved heat transfer material.